[Why]
In order to switch over the inbox from region4 to cw4 we need to know if
the firmware is capable of properly invalidating the cache before
reading the commands.

Easiest way is to just check the firmware version, but we don't have the
helper macros or a way for the dmub_srv to know what version it is.

[How]
Add a new fw_version field to the creation parameters that driver can
optional pass in. Assumes a version of 0x00000000 is invalid.
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>